Rapid charging and power management of a battery-powered fluid analyte meter

ABSTRACT

A system and method is described for rapid charging and power management of a battery for a meter. A charger component is operably associated with the meter and is capable of executing a rapid charge algorithm for a rechargeable battery. The algorithm includes monitoring for a connection to an external power source and implementing a charging routine of a battery at a first charge rate and then at a second charge rate. The second charge rate is lower than the first charge rate. A temperature rise in the rechargeable battery due to the first charge rate has a negligible heat transfer effect on the fluid sample. The meter can also include a power switch for controlling current flow to a battery fuel gauge. The power switch is open when the meter enters into a sleep mode. The state of battery charge is determined after the meter exits the sleep mode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/058,711, filed Mar. 2, 2016, now allowed, which is a continuation ofU.S. patent application Ser. No. 13/789,104, filed Mar. 7, 2013, nowU.S. Pat. No. 9,312,720, which is a continuation of U.S. patentapplication Ser. No. 13/436,416, filed Mar. 30, 2012, now U.S. Pat. No.8,441,363, which is a continuation of U.S. patent application Ser. No.12/129,185, filed May 29, 2008, now U.S. Pat. No. 8,164,468, whichclaims priority to and the benefits of U.S. Patent Application No.61/012,690, filed Dec. 10, 2007, each of which are hereby incorporatedby reference herein in their entireties.

FIELD OF THE INVENTION

The present invention generally relates to test sensors powered by arechargeable battery, and more particularly, to rapid charging and powermanagement of a battery-powered sensor.

BACKGROUND OF THE INVENTION

The quantitative determination of analytes in body fluids is of greatimportance in the diagnoses and maintenance of certain physicalconditions. For example, lactate, cholesterol, and bilirubin should bemonitored in certain individuals. In particular, determining glucose inbody fluids is important to individuals with diabetes who mustfrequently check the glucose level in their body fluids to regulate theglucose intake in their diets. The results of such tests can be used todetermine what, if any, insulin or other medication needs to beadministered. In one type of testing system, test sensors are used totest a fluid such as a sample of blood.

Many individuals test their blood glucose several times per day. Thus,the individuals often must carry with them a meter for determining theglucose concentration of their blood. The individuals may also carrywith them other analyte-testing instruments, including test sensors, alancet, disposable lancets, a syringe, insulin, oral medication,tissues, or the like. Thus, the individuals are able to perform testingof their blood glucose at different locations including their homes,places of employment (e.g., office buildings or work sites), places ofrecreation, or the like. Carrying the meter and/or other analyte-testinginstruments to these various locations may be inconvenient.

Blood glucose meters can be powered using various types of poweringconfigurations such as batteries or adapters that can be plugged into astandard outlet. The use of batteries allows the device to be portableand mobile without using a power outlet. Batteries available for use inblood glucose meters include both disposal batteries and rechargeablebatteries. The use of a rechargeable battery for a blood glucose meterrequires the battery to have a charge for the meter to function.Sometimes when a battery is discharged, a critical situation may arisethat requires an emergency blood glucose test.

Measurement of blood glucose concentration is typically based on achemical reaction between blood glucose and a reagent. The chemicalreaction and the resulting blood glucose reading as determined by ablood glucose meter is temperature sensitive. Therefore, a temperaturesensor is typically placed inside a blood glucose meter. The calculationfor blood glucose concentration in such meters typically assumes thatthe temperature of the reagent is the same as the temperature readingfrom the sensor placed inside the meter. However, if the actualtemperature of the reagent and the meter are different, the calculatedblood glucose concentration will not be accurate. An increase intemperature or the presence of a heat source within a blood glucosemeter will generally result in an erroneous measurement of bloodglucose.

Power management in a battery-powered blood glucose meter can includeusing a battery fuel gauge to monitor the state of battery charge. Abattery fuel gauge typically monitors, on a continual basis, the currentflowing in both directions through the battery of the meter. However,such continuous monitoring also requires the battery fuel gauge tooperate constantly, which results in increased power consumption, evenwhen the battery-powered blood glucose meter is in a sleep mode. Theincreased power consumption requires a larger battery size and increasesbattery cost, particularly for portable devices.

It would be desirable to have a battery-powered meter that can be rapidcharged without a significant temperature rise. It would also bedesirable to manage the power consumption of a battery-powered meter tominimize power consumption during periods of non-use while maintainingan accurate assessment of the state of battery charge.

SUMMARY OF THE INVENTION

According to one embodiment, a battery-powered meter is adapted todetermine an analyte concentration of a fluid sample using a testsensor. The meter includes a port sized to receive at least a portion ofa test sensor. A front portion comprises a display operable to displaythe analyte concentration of the fluid sample. A user-interactionmechanism is operable to control the meter. The meter also includes ahousing for a rechargeable battery. A battery charger component isoperably associated with the meter. The battery charger component iscapable of executing a rapid charge algorithm for a rechargeablebattery. The algorithm comprises monitoring for a connection to anexternal power source. If the external power source is detected, acharging routine is implemented for the rapid charging of a battery at afirst charge rate until a first predetermined event occurs followed bycharging the battery at a second charge rate until a secondpredetermined event occurs. The second charge rate is lower than thefirst charge rate.

According to another embodiment, a method of rapid charging a battery ina fluid analyte meter includes monitoring for a connection to anexternal power source. A rapid charge routine is implemented forcharging the battery at a first charge current rate over a firstpredetermined time period. Following the first predetermined timeperiod, a normal charge routine is implemented for charging the batteryat a second charge current rate over a second predetermined time period.The first charge current rate is greater than the second charge currentrate. The first predetermined time period is at least partially based onan approximated temperature rise in the battery due to a charge currentassociated with the first charge current rate.

According to a further embodiment, a computer-readable medium is encodedwith instructions for directing a rapid charge of a battery for a meteroperable to determine an analyte concentration of a fluid sample. Theinstructions include monitoring for a connection to an external powersource and implementing a rapid charge routine for charging the batteryat a first charge current until a first predetermined event occurs.Following the occurrence of the first predetermined event, a normalcharge routine is implemented for charging the battery at a secondcharge current until a second predetermined event occurs. The firstcharge current is greater than the second charge current. Thetemperature rise is monitored for at least one of the battery and themeter, with the monitoring occurring at one or more predetermined timeintervals. If the temperature rise in the battery or the meter exceed apredetermined threshold value, the rapid charge routine or the normalcharge routine are canceled.

According to another embodiment, a portable meter having a circuit isconfigured with a battery to provide power to a sensing element withinthe circuit. The meter includes a processor powered by the circuit. Theprocessor is configured to operate the meter in an active mode and asleep mode. A fuel gauge is powered by the circuit. The fuel gauge isconfigured to track state of battery charge data received from thebattery during active mode operation of the meter. An interface isconfigured to transfer state of battery charge data from the fuel gaugeto the processor. A power switch controls current flow to the fuel gaugeand is configured to be open and closed by the processor. The processorsignals the power switch into an open position if the meter enters intothe sleep mode and the processor signals the power switch into a closedposition if the meter enters into an active mode. Prior to entering thesleep mode, the processor is configured to record a first state ofbattery charge for the battery and a first time reference immediatelyprior to the meter entering said sleep mode. The processor is furtherconfigured to determine a second state of battery charge at a secondreference time immediately after the meter exits from the sleep modeinto the active mode. The second state of battery charge is determinedbased on the recorded first state of charge, the first reference time,the second reference time, and a predetermined energy usage rate of themeter during the sleep mode.

According to another embodiment, a method of power management includes abattery-powered meter that is configured to operate in an active modeand a standby mode. The batter-powered meter includes a battery fuelgauge and a microcontroller. The method includes the steps of receivinga first request to enter into the standby mode. A first state of chargeis recorded for a battery of the meter. The recording occurs at a firstreference time immediately after the first request is received. Thefirst reference time is recorded using the microcontroller. The meter isentered into the standby mode with the power to the battery fuel gaugebeing switched off in the standby mode. A second request to exit thestandby mode and enter the active mode is received at a second referencetime. The second reference time occurs after the first reference time.In response to the second request, a second reference time isimmediately recorded and the microcontroller determines a second stateof battery charge based on the first reference time, the secondreference time, a standby mode current, and a standby mode voltage ofthe meter.

According to a further embodiment, a computer-readable memory medium hasstored thereon instructions for managing the power of a battery-poweredmeter operating in an active mode and a sleep mode. The instructionsincludes the steps of receiving a first request to enter into the sleepmode and recording a first state of charge for a battery of the meter.The recording occurs at a first reference time immediately after thefirst request is received. A first reference time is recorded. The meteris entered into the standby mode wherein power to a battery fuel gaugeis switched off in the standby mode. A second request is received at asecond reference time to exit the sleep mode and enter the active mode.The second reference time occurs after the first reference time.Immediately after the second request, a second reference time isrecorded. A second state of battery charge is determined based on thefirst reference time, the second reference time, a sleep mode current,and a sleep mode voltage.

Additional aspects of the invention will be apparent to those ofordinary skill in the art in view of the detailed description of variousembodiments, which is made with reference to the drawings, a briefdescription of which is provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a illustrates a sensor including a lid according to oneembodiment.

FIG. 1b illustrates the sensor of FIG. 1a without the lid.

FIG. 2a illustrates a front view of a meter with a display according toone embodiment.

FIG. 2b illustrates a side view of the meter from FIG. 2 a.

FIG. 3 illustrates a charging circuit for a rechargeable batteryaccording to one embodiment.

FIG. 4 illustrates a charging algorithm having a high temperature-risephase used to charge a battery.

FIG. 5 illustrates a current regulation phase having a high and lowtemperature-rise phase according to one embodiment.

FIG. 6 illustrates a finite state machine of a method to rapid-charge arechargeable battery that minimizes temperature rise according to oneembodiment.

FIG. 7 illustrates a battery charge profile according to one embodiment.

FIG. 8 illustrates a circuit for a meter with a fuel gauge and batterycharger according to one embodiment.

FIG. 9 illustrates a finite state machine of a power management methodfor a battery-powered device according to one embodiment.

While the invention is susceptible to various modifications andalternative forms, specific embodiments are shown by way of example inthe drawings and are described in detail herein. It should beunderstood, however, that the invention is not intended to be limited tothe particular forms disclosed. Rather, the invention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention.

DETAILED DESCRIPTION

A system and method for rapid charging of a battery for a meter isdisclosed herein. When the rechargeable battery for a battery-poweredmeter becomes discharged, a critical situation arises for a user in theevent that an emergency test is needed, such as, for example, when usinga blood glucose meter. Such a critical situation can be minimized formeters powered with rechargeable batteries. A discharged battery can becharged for a very short period of time using a rapid charge techniqueto provide enough of a charge to energize the meter to complete one ormore tests, such as analyzing blood glucose concentration, whileminimizing temperature rise in the meter.

FIGS. 1a-b and FIGS. 2a-b illustrates certain embodiments of meters,such as blood glucose meters, according to the present disclosure. Thedevices can contain electrochemical test-sensors that are used todetermine concentrations of at least one analyte in a fluid. Analytesthat may be determined using the device include glucose, lipid profiles(e.g., cholesterol, triglycerides, LDL and HDL), microalbumin,hemoglobin A₁C, fructose, lactate, or bilirubin. The present inventionis not limited, however, to devices for determining these specificanalytes and it is contemplated that other analyte concentrations may bedetermined. The analytes may be in, for example, a whole blood sample, ablood serum sample, a blood plasma sample, or other body fluids like ISF(interstitial fluid) and urine.

Although the meters of FIGS. 1 and 2 are shown as being generallyrectangular, it should be noted that the cross section of the metersused herein may be other shapes such as circular, square, hexagonal,octagonal, other polygonal shapes, or oval. A meter is typically made ofa polymeric material. Non-limiting examples of polymeric materials thatmay be used in forming the meter include polycarbonate, ABS, nylon,polypropylene, or combinations thereof. It is contemplated that themeter may be made using non-polymeric materials.

According to certain embodiments, the test-sensors for the devices aretypically provided with a capillary channel that extends from the frontor testing end of the sensors to biosensing or reagent material disposedin the sensor. When the testing end of the sensor is placed into fluid(e.g., blood that is accumulated on a person's finger after the fingerhas been pricked), a portion of the fluid is drawn into the capillarychannel by capillary action. The fluid then chemically reacts with thereagent material in the sensor so that an electrical signal indicativeof the analyte (e.g., glucose) concentration in the fluid being testedis supplied and subsequently transmitted to an electrical assembly.

Reagent materials that may be used to determine the glucoseconcentration include glucose oxidase. It is contemplated that otherreagent material may be used to determine the glucose concentration suchas glucose dehydrogenase. If an analyte other than glucose is beingtested, different reagent material will likely be used.

One example of a test-sensor is shown in FIGS. 1a, 1b . FIGS. 1a, 1bdepict a test-sensor 70 that includes a capillary channel 72, a lid 74,and a plurality of electrodes 76, 78, and 80. FIG. 1b is illustratedwithout a lid. The plurality of electrodes includes a counter electrode76, a detection electrode 78, and a working (measuring) electrode 80. Asshown in FIG. 1b , the test-sensor 70 includes a fluid-receiving area 82that contains reagent. It is contemplated that other electrochemicaltest-sensors may be employed.

Referring to FIGS. 2a-b , one example of a meter 100 is illustratedaccording to an embodiment of the present disclosure. The meter 100 isdesirably sized so that it may fit generally within a user's purse orpocket. Thus, it is desirable, though not necessary, that the meter 100have a long-dimension of less than approximately 2 to 3 inches toenhance portability. It is also desirable that the meter 100 have afootprint area of less than about 6 to 9 in². The meter 100 may evenhave a footprint area in the range of about 3 in².

As shown in FIGS. 2a and 2b , the meter 100 includes a display 102visible through a front portion 120, a test-sensor dispensing port 104,and a user interface mechanism 106. The user interface mechanism 106 maybe buttons, scroll wheels, etc. FIG. 2a shows the meter 100 with anumber of display segments. After a user places a fluid (e.g., blood) ona test-sensor, the analyte (e.g., glucose) level is determined by themeter 100, which displays the reading on the display 102.

The meter 100 typically includes a microprocessor or the like forprocessing and/or storing data generated during the testing procedure.For example, the user-interface mechanism 106 a-b may be depressed toactivate the electronics of the meter 100, to recall and view results ofprior testing procedures, to input meal and/or exercise indicators, orthe like. The meter 100 may also use the same or a differentmicroprocessor for power management, including executing routines tocontrol recharging functions of the meter 100 for battery-powereddevices.

The test sensor dispensing port 104 is adapted to receive and/or hold atest sensor and assist in determining the analyte concentration of afluid sample. To communicate at least the analyte concentration to theuser, the meter 100 includes a display 102. One example of a display 102that may be used in the meter 100 is a liquid-crystal display. Theliquid-crystal display typically shows information from the testingprocedure and/or in response to signals input by the user-interfacemechanism 106 a-b. Other types of displays can include, for example,light emitting diode (LED), organic light emitting diode (OLED),liquid-crystal display (LCD) with backlight, thin film transistor (TFT),a segmented display or other types of transmissive displays. The type ofdisplay can have minimal or significant effects on the amount of energyused by a meter.

The meter 100 may be powered by a main power supply, a battery, or anyother suitable power source. The main power supply may includeinternally operated AC and/or DC power supplies. It can be desirablethat the meter 100 be powered by battery due to the portable nature ofthe meter 100. A battery housing 130 may be located in a back portion122 of a meter 100 or within the front portion 120.

In certain embodiments, the battery for the meter 100 is rechargeablevia a main power source that can be connected to the meter 100 through apower adapter receptacle 124. Different types of rechargeable batteryconfigurations may be used to power the meter 100 including, forexample, lithium ion (Li-Ion), lithium polymer (Li-Po), nickel cadmium(NiCd) or nickel metal hydride (NiMH).

For certain meter 100 configurations, a rechargeable battery (not shown)is removed from the battery housing 130 of the meter 100 and placed intoa separate charger that is, for example, plugged into a standard AC walloutlet or connected to a car battery. Other meters can be charged byplugging one end of a special adapter into the power adapter receptacle124 of the meter 100 while the battery remains in the battery housing130. A second end of the special adapter is then plugged into the ACpower outlet to charge the battery. In certain embodiments, the meter100 may be powered by connecting one end of the special adapter to asource on a computer, such as a Universal Serial Bus (USB) port, and thesecond end to the power adapter receptacle 124.

Battery chargers are capable of providing a fast or rapid charge to arechargeable battery by using a higher charging current than would betypically used to charge the battery, with minimal degradation of thebattery. This principal of rapid charge of a battery also applies tobattery charger integrated circuits. For example, rechargeablebatteries, such as Li-Ion, LiPo, NiCd and NiMH, allow a fast chargingrate of up to approximately 2C to 5C without a significant reduction inbattery life. The term C is defined as the rated capacity of the givenbattery that is being charged. For example, a battery with a 200 mAhcapacity has a 1C rate of 200 mA, a 2C rate of 400 mA and a 5C rate of1,000 mA. In certain embodiments, a very short charge time for a batteryat a high charging rate can provide sufficient energy to a meter batteryto allow for several fluid analyte concentration tests.

In certain embodiments, a device may issue an early warning alert that,for example, approximately ten fluid analyte concentration tests can becompleted with the remaining charge in the battery. The device mayfurther issue a final alert indicating that, for example, two or fewertest can be completed based on the remaining charge. In such situations,it would be beneficial to charge the battery at a high charging rate fora very short charge time, particularly after the final alert.

An example demonstrating the amount of energy used in a single analyteconcentration test is provided for meters similar to the embodimentsdescribed herein. Assuming the test takes up to two minutes and that thedisplay 102 for the meter 100 is running continuously during this time,the meter 100 having a transmissive display (e.g., OLED, LCD withbacklight, TFT) can consume approximately up to 40 milliamperes (mA)from the rechargeable battery at 3.6 volts (V). The equation belowmathematically shows the relationship of the energy consumed by themeter relative to the duration of the test, the battery voltage, and thecurrent:E _(FROM BATTERY) =I×V _(BAT) ×t _(OPERATION)

where:

-   -   E_(FROM BATTERY) is the energy consumption    -   V_(BAT) is the voltage of the battery    -   I is the current drawn by the meter    -   t_(OPERATION) is the duration of the analyte concentration test        Applying the values from the example above:        E _(FROM BATTERY)=40×10⁻³ A×3.6 V×2 min×60 sec≈17 J

Another example demonstrates a rapid charge scenario for a rechargeablebattery for a meter similar to the embodiments described herein. Themeter can be plugged into a power source using a special adapter thatmay be connected to a USB port or into another power source. In thisexample, an internal battery charging circuit provides a charging rateof 2C. After the battery has been charged, for example, for certainperiod of time, I_(CHARGING) (e.g., 30 seconds, one minute), the energyreceived from the battery charger is approximated by the followingrelationship:E _(CHARGED) =I _(CHARGING) ×V _(BAT) ×t _(CHARGING)

where:

-   -   E_(CHARGED) is the energy received from the battery charger    -   V_(BAT) is the voltage of the battery    -   I_(CHARGING) is the charging current (e.g., for 200 mAh battery        I_(CHARGING)=400 mA at a charge rate of 2C)    -   t_(CHARGING) is the charge duration (e.g., one minute in our        example)        Applying the values from the example above:        E _(CHARGED)=0.4 A×3.6 V×60 sec=86.4 J        This example demonstrates that after charging the battery for        approximately 60 seconds at a 2C current rate, enough energy can        be provided to a rechargeable battery to perform approximately        five tests (86.4 J/17 J≈5) based on the single test energy draw        example demonstrated above, for which the energy consumption of        one test was calculated to be 17 Joules.

The use of rapid charging for a meter battery can lead to an increase inthe temperature of the meter and change the resulting analyteconcentration reading that is output by the meter. Therefore, whilerapid charging is desirable for temperature sensitive meters, such as,for example, meters having rechargeable batteries, it is furtherdesirable to minimize temperature rise for the device.

The embodiments described herein allow for the rapid charging of thebattery for a meter performing temperature-sensitive tests, such asportable meters, using a power source for rapid charging the battery fora short period of time. In certain embodiments, the charging processcontinues at a normal charge rate after the rapid charging is completed.The embodiments desirably minimize the temperature rise of the meter.

In certain embodiments, the internal charging circuit for the meter mayhave a rapid charge mode and a normal charge mode. An internal chargingcircuit can further limit the temperature rise of the meter by reducingthe charging rate from a rapid charge rate to a normal charge rate thathas a negligible temperature rise. Such an embodiment can beparticularly beneficial when a user does not unplug the special adapterfrom the power source following a rapid charge.

In certain embodiments, once a meter battery is connected to an externalpower source, such as a USB port or a power adapter, the internalcharging circuit or battery charger can first go into a rapid chargemode, and subsequently switch to a normal or reduced charge modeaccording to the temperature rise criteria for the particular portabletemperature-sensitive meter. For example, the rapid charge mode can havea charging rate up to approximately 5C. In other embodiments, thecharging rate may exceed 5C. The charge rate will vary on such criteriaas the configuration of the battery or the current output of the powersource (e.g., USB port or power adapter). In the example of a lithiumion battery, the maximum charging rate is approximately 2C. In theexample of a USB port, the current capability may be either 100 mA or500 mA.

In certain embodiments, when the rapid charge of the rechargeablebattery is complete, an internal electronic circuit can provide aperceivable signal to the user, such as an audio or light signal. Thesignal will let the user know that the battery has sufficient energy topower the desired test(s). At this point, the user will have the optionof unplugging the meter from the power source and performing the analyteconcentration test. If the user does not unplug the meter from the powersource, the charging circuit for the meter can be configured to switchinto a normal charge mode that provides, for example, a charging rate inthe range of approximately 0.5C to 1C. In the normal charge mode, lessheat is generated to the battery than with the higher charging rate ofthe rapid charge mode. In certain embodiments, the normal charge modecan be set to a charge current level that allows an equilibrium betweenheat dissipation due to charging and heat irradiation from thetemperature-sensitive meter to the surrounding atmosphere (e.g., air).In certain embodiments, it is desirable to maintain the temperature inthe normal charge mode that was achieved during the rapid charge mode.

Referring now to FIG. 3, a schematic of a charging circuit 300 for arechargeable battery 310 is illustrated according to certainembodiments. The charging circuit 300 experiences a battery temperaturerise during the charging of the battery 310, similar to what beexperienced during the charging of a meter battery. The battery 310 hasan internal equivalent series resistance (ESR) 312 that causes the heatdissipation of the battery. Furthermore, a temperature rise in thebattery 310 will be proportional to the charge time and to the secondorder of the charge current. ESR varies according to the type ofbattery. For example, a lithium polymer battery that is 50 percentdischarged has a typical equivalent series resistance of approximatelyless than 0.07 Ohms. The charging circuit 300 further includes a charger330, such as an external power source, connected to the battery 310.

Another example demonstrates an approximation of the amount of heatgenerated in a battery in a rapid charge mode. Assuming a lithium ionbattery, such as the one discussed above having a current rate of 2C anda capacity of 200 mAh, the value for the charging current is calculatedas follows:I _(CHG)=2×200=400 mA=0.4 AThe power dissipation, or heat caused by the internal equivalent seriesresistance 312 of battery 310 during the charging process, can becalculated using the following relationship:P=I _(CHG) ² ×ESRApplying the values from above, the battery power dissipation is:P _(DISP)=(0.4 A)²×0.07=0.012 WThe energy dissipation for an assumed 60 second rapid charge iscalculated to be 0.72 Joules using the following relationship:Q=P _(DISP) ×t=0.012 W×60 sec=0.72 J

The general relationship for the heat transferred is express as:Q=m×(ΔT)×C _(P) (J)

where

-   -   Q=heat transferred;    -   ΔT=the change in temperature;    -   Cp=the specific heat of the battery; and    -   m=mass.        The specific heat will vary depending on the type of        rechargeable battery that is used. The specific heat, in the        example of a lithium polymer battery made from mixed        plastic/foil/fiber materials, is within 1 to 3 J/gram ° C. To be        conservative in calculating temperature rise, the lower value of        the specific heat will be used. The mass for a typical 200 mAh        lithium polymer battery is about 5 grams. Applying the above        values and results, the heat transfer relationship yields a        temperature rise of:

${\Delta\; T} = {\frac{Q(J)}{m \times C_{P}} = {\frac{0.72\; J}{5 \times 1} = {0.14{^\circ}\mspace{20mu}{C.}}}}$

In the above example, which is applicable to rapid charging scenariosthat can occur in certain embodiments, a temperature rise of 0.14° C. orless can be considered to be negligible and would not be expected toaffect an analyte concentration reading. In other embodiments, atemperature rise of approximately 1° C. or less may be considerednegligible for analyte concentration testing of a fluid sample.Furthermore, the above example conservatively estimates a highertemperature rise than would be expected since the heat transfer betweenthe meter and air was not subtracted from the calculated result nor wasthe temperature rise calculated based on the entire battery-metersystem. Rather the temperature rise calculation was conservativelyestimated for the battery only.

The above calculation is based on a series of calculations using anassumed 60 second rapid charge time along with other assumed factors. Asthe calculations demonstrate, a shorter rapid-charge time of, forexample, thirty seconds at a 2C charge rate provides enough energy formore than one test of an analyte concentration for the assumed meter.

Referring now to FIGS. 4 and 5, a standard charging algorithm isillustrated in FIG. 4 and embodiments of a rapid charge algorithm aredisclosed in FIG. 5. The charging sequences for the algorithms of FIGS.4 and 5 begin with a pre-conditioning phase, then progress to a currentregulation phase, and close with voltage regulation and terminationphases, after which charging of the battery is considered complete. Therapid charge algorithm of FIG. 5 further breaks up the currentregulation phase into two separate steps. The current regulation phasestarts out in a rapid charge mode or high current regulation phasehaving a high temperature rise and after the lapse of a predeterminedperiod of time or after a predetermined charge voltage is achieved, thecharge current will decrease or move into a low current regulationhaving a low temperature rise.

For both FIGS. 4 and 5, as long as the battery is receiving energy fromthe battery charger, the battery can continue charging until the batteryreaches a regulation voltage at which point the charge current decreasesuntil the charge is considered complete. The difference between FIGS. 4and 5 is that the current charge remains constant in the standardcharging algorithm (FIG. 4) from the time the minimum charge voltage isreached up until the time the regulation voltage is reached. However, inthe rapid charge algorithm the charge current rises for a short periodafter the minimum charge voltage is reached and then the charge voltagedrops, so that the temperature rise is minimized to a point of beingnegligible to any temperature sensitive tests that may be conducted withthe meter. The charge time for the algorithm of FIG. 5 can be longerthan the standard charging algorithm illustrated in FIG. 4.

Referring now to FIG. 6, an embodiment of a finite state machine isillustrated for rapid charging of a meter battery. The embodiment ofFIG. 6 can be implemented, for example, using a controller ormicroprocessor. The meter starts in a standalone mode or no chargingmode at step 600 in which the meter is not connected to a power sourcesuch as, for example, a power adapter or USB port. The meter isconnected to a power source at step 605, which in turn, can initiate acharging algorithm in a meter having a rechargeable battery. In certainembodiments, the battery begins charging at a rapid charge rate at step610 in which the current is regulated at, for example, a charge currentof 2C to 5C. The rapid charge rate continues for a predetermined periodof time at step 615, such as, for example thirty seconds or one minute.The rapid charge period can also be determined based on the batteryachieving a threshold charge voltage without exceeding, for example, acertain time period or temperature rise.

During the rapid charge stage 610, an assessment may be made whether thebattery temperature is too high at step 625 through monitoring of atemperature sensor. In certain embodiments, if it is established thatthe battery temperature is too high at step 625, the charging processcan be stopped and a determination made at step 630 whether a chargerand/or battery failure has occurred. At this point, the meter can returnto the stand alone mode at step 600 and corrective action can be taken.In certain embodiments, once the threshold time period or voltage isreached at step 620, an audible or visible alarm or other signal at step635 can be used to alert the user that the rapid charge is complete.

The rapid charge method of the finite state machine can then enter anormal charge phase at step 640 in which the charge current is reduced.In certain embodiments, the meter may then be disconnected from thepower source at step 645. Another assessment can also be made at thisstage of whether the battery temperature is too high at step 650, whichmay lead to the charging process being stopped and a determination madeat step 630 whether a charger and/or battery failure has occurred.During the normal charge mode, a routine can also assess at step 655whether the battery voltage exceeds a threshold value. If a thresholdvoltage is exceeded, the charging can enter a constant voltageregulation phase at step 660. In certain embodiments, the meter may bedisconnected from the power source at step 665. A further assessment canalso be made at this point of whether the battery temperature is toohigh at step 670, which again, may lead to the charging process beingstopped and a determination made at step 630 whether a charger and/orbattery failure has occurred. In certain embodiments, a routine canperiodically check whether the charge current exceeds a certainthreshold value at step 675. If the charge current exceeds the thresholdvalue, the charging routine can continue in the constant voltageregulation phase at step 660. If the charging current is less than apredetermined threshold value at step 680, the user can be signaled atstep 685 using, for example, an audible or visual cue that charging forthe battery or system is complete. The meter can at this point enterinto a standby mode at step 690 with the charging process completed. Theuser may at this point unplug the meter at step 695 from the powersource at which point the meter returns to the stand alone mode at step600.

The embodiments disclosed herein for the rapid charging of a battery fora temperature-sensitive meter provide a number of benefits. For example,instead of constantly charging a battery at high constant rate until thevoltage reaches a predefined level, the battery is being charged at thehigh rate only for a short period of time to provide enough energy for alimited number of blood glucose concentration tests. After rapidcharging, the charger may switch into low-rate or normal charging modethat maintains the battery temperature as it was at the end of rapidcharging phase. The embodiments disclosed herein allow a user, in theexample of a meter, to enjoy the benefits associated with using a meteroperating on a rechargeable battery while further allowing the user toquickly recharge the meter without sacrificing test accuracy caused bytemperature rise.

In certain embodiments, the temperature rise can be monitored atpredetermined periodic intervals for the battery or the meter. If thetemperature rise in the battery of the meter exceeds a predeterminedthreshold value, the rapid charge routine or the normal charge routinecan be cancelled. Such a temperature rise may be indicative of a failurein the meter device or the battery.

In certain embodiments, a battery-powered meter is adapted to determinean analyte concentration of a fluid sample using a test sensor. Themeter includes a test port or opening sized to receive at least aportion of the test sensor. A front portion has a display operable todisplay the analyte concentration of the fluid sample. Auser-interaction mechanism can be used to control the meter. A housingcan be provided for holding a rechargeable battery. A battery chargercomponent can be operably associated with the meter and can furtherexecute a rapid charge algorithm for a rechargeable battery. In oneembodiment, the algorithm includes: (i) monitoring for a connection toan external power source, and (ii) if the external power source isdetected, implementing a charging routine for the rapid charging of abattery at a first charge rate until a first predetermined event occursfollowed by charging said battery at a second charge rate until a secondpredetermined event occurs. The second charge rate is lower than thefirst charge rate. In other embodiments, a temperature rise in therechargeable battery due to the first charge rate has a negligible heattransfer effect on the fluid sample.

In other embodiments, the battery-powered meter is a blood glucosemeter. The battery-powered meter can have a first charge rate rangingfrom 2C to 5C. The battery-powered meter can also have a second chargerate that is less than 1C. The battery charger component can also be apart of an integrated circuit.

In other embodiments, the first predetermined event for thebattery-powered meter is a lapsing of a predetermined time period. Thepredetermined time period can be approximately one minute or less. Thefirst predetermined event for the battery-powered meter can also beexceeding a predetermined charge voltage or exceeding a thresholdtemperature in the rechargeable battery. The first predetermined eventfor the battery-powered meter can also be exceeding a thresholdtemperature in the meter.

In other embodiments, the external power source for the battery-poweredmeter can be a port on a computing device. The rechargeable battery canalso be periodically monitored for elevated temperature readings.

In certain embodiments, a method of rapid charging a battery in a bloodglucose or other fluid analyte meter includes monitoring for aconnection to an external power source and implementing a rapid chargeroutine for charging the battery at a first charge current rate over afirst predetermined time period. Following the first predetermined timeperiod, the method further includes implementing a normal charge routinefor charging the battery at a second charge current rate over a secondpredetermined time period. The first charge current rate is greater thanthe second charge current rate. The first predetermined time period isat least partially based on an approximated temperature rise in saidbattery due to a charge current associated with the first charge currentrate.

In other embodiments, the first predetermined time period for the methodis at least partially based on a threshold charge voltage. The meter canalso have a liquid crystal display and the threshold charge voltage canbe sufficient to conduct five or fewer blood glucose concentrationtests. The first charge current rate and second charge current rate canalso be generally constant.

In other embodiments, the method also includes notifying a user of theblood glucose meter with a perceivable signal following the firstpredetermined time period. A termination charge routine can also beimplemented following the second predetermined time period that chargesthe battery at a third current rate until a predetermined event occurs,with the third charge current rate being lower than the second chargecurrent rate. The third charge current rate can also be continuouslydecreasing.

In certain embodiments, a computer-readable medium is encoded withinstructions for directing a rapid charge of a battery for a meter, suchas a blood glucose meter. The meter will generally be conductingtemperature-sensitive testing, such as determining an analyteconcentration of a fluid sample. The instructions can include monitoringfor a connection to an external power source. A rapid charge routine oralgorithm can then be implemented for charging the battery at a firstcharge current until a first predetermined event occurs, such as thelapse of a certain time period or reaching a certain threshold voltage.Following the occurrence of the first predetermined event, a normalcharge routine or algorithm can be implemented for charging the batteryat a second charge current until a second predetermined event occurs.The first charge current is greater than the second charge current.

It is contemplated that certain embodiments of battery-powered meters,such as systems for testing blood glucose concentrations, can include abattery fuel gauge. For example, a battery fuel gauge integrated circuitcan be incorporated into the system to determine the status of thecharge for a battery. It is further contemplated that battery chargeinformation can be used by a power management routine operating withinthe battery-powered meter system. The power management routine can allowthe meter to operate over extended periods of time by managing powerduring periods of use and non-use. For example, a power managementroutine in a battery-powered blood glucose meter can allow for use ofthe meter over longer periods of time without having to recharge thebattery by controlling power consumption during periods blood glucoseconcentration is analyzed and during periods between such analyses.

As described previously in the exemplary embodiment illustrated in FIG.2, different types of rechargeable battery configurations may be used topower a meter including, lithium ion (Li-Ion), lithium polymer (Li-Po),nickel cadmium (NiCd), or nickel metal hydride (NiMH) batteries. The useof a lithium-based battery can provide certain benefits in the meteroperation because the voltage across a lithium battery does nottypically drop significantly during meter operation, that is, during thedischarge process.

FIG. 7 illustrates a battery discharge profile according to certainembodiments of the present application. The discharge profileillustrates the change in load voltage for a Li-Po battery duringbattery discharge during the operation of a meter, such as a bloodglucose meter. The illustrated Li-Po battery has a fully-charged voltageof approximately 4.1 Volts. Discharge profiles are shown for the batteryoperating at 20, 50, and 100 percent of its rated capacity (C), that is,0.2C, 0.5C, and 1C, respectively. For example, with the Li-Po batteryoperating at 0.5C, and over the range shifting from 40 percent of itsremaining charge to 20 percent of its remaining charge, the Li-Pobattery experiences a voltage change of approximately 40 millivolts orless. Even with fluctuations in the discharge current ranging frombetween 0.2C and 1C, voltage change in the illustrated Li-Po battery mayspan a 100 millivolt range. For an initial discharge current of 0.5C,this may mean a voltage change of ±50 millivolts for shift in thedischarge current down to 0.2C, or up to 1C. As further illustrated inFIG. 7, the load voltage for a Li-Po battery, such as one that may beused in a meter, can decrease significantly when less than five percentof the charge remains.

A battery fuel gauge can be beneficial for certain battery-powereddevices—for example, portable meters using lithium batteries—becausetraditional direct voltage measurement methods that determine the stateof battery charge do not typically work well for Li-Po or Li-Ionbatteries. As illustrated, for example, in FIG. 7, the voltage across alithium battery does not vary significantly during the discharging stageof the battery. To assess the remaining charge becomes difficult becauseof the small voltage changes in the lithium battery in which voltagechanges can be attributed to the load placed on the battery by thebattery-powered device or to the battery discharging. A battery fuelgauge can continuously monitor the current flowing through a battery inboth directions—charging and discharging—counting, for example, thenumber of Coulombs the battery receives during charging and the numberof Coulombs the battery loses during discharging.

FIG. 8 illustrates a circuit including a battery charger 801 with a fuelgauge 803 that can be applied to a meter, such as, for example, a bloodglucose meter, according to certain embodiments of the presentdisclosure. The battery charger can be coupled with a primary powersource 811. The primary power source may be a power outlet, a generator,an AC/DC wall-mount adapter, a USB port, or other power source capableof providing sufficient power to charge a battery. The battery charger801 is connected to the positive electrode of a battery 802. Thenegative electrode of the battery 802 is coupled to ground 820 by way ofa sensing resistor 807. As illustrated in FIG. 8, a microcontroller 805and a fuel gauge 803 can be powered using a voltage regulator 804. Theconfiguration of the voltage regulator 804 relative to the batterycharger 801 and the battery 802 allows the voltage regulator to alwaysreceive power from either the battery charger 801—e.g., when the systemis charging the battery—or the battery 802—e.g., when the system isdischarging. An interface 813 between the microcontroller 805 and thefuel gauge 803 allows the transfer of information between the twodevices so that the state of charge of the battery 802 can bedetermined. The microcontroller 805 can include a real-time clock andcan further receive and process data from the fuel gauge 803. After thedata from the fuel gauge is processed by the microcontroller 805, themicrocontroller 805 can indicate the state of charge of the battery 802on a display 806.

The embodiment illustrated in FIG. 8 allows a charging process in whichcurrent flows from the battery charger 801 to the battery 802. Duringthe charging process, the current continues from the battery 802 toground 820 by way of the sensing resistor 807. During the chargingprocess, fuel gauge 803 monitors the voltage across sensing resistor 803to determine the number of Coulombs that battery 802 receives frombattery charger 801. When charging of the battery 802 is complete, thebattery charger 801 sends a signal 812 to the microcontroller 805 thatthe battery charge is complete. The communication between the batterycharger 812 and the microcontroller 805 that charging is completefurther includes synchronizing the microcontroller 805 with the fuelgauge 803. Simultaneous or near simultaneous with thebattery-charge-complete signal 812, the microcontroller can communicatewith the display 806 so that a “Charge Complete” text, or an iconillustrating that the charge is complete, is shown in the display 806.

The battery charger 801 can be disconnected from the primary powersource 811. When this occurs, the battery 802 then becomes the onlysource of power for the circuit illustrated in FIG. 8. Furthermore, uponthe disconnection from the primary power source 811, the direction ofcurrent, previously flowing from the battery to the sensing resistor807, changes or reverses. At this point, too, the fuel gauge 803instantly or nearly instantly detects the reversed polarity of thevoltage across the sensing resistor 807. The reversed polarity in thesensing resistor 807 triggers the fuel gauge 803 to start tracking thecurrent out of the battery 802 by counting the energy units—that is,Coulombs—that leave the battery 802 as the battery is discharging.During the discharge phase of the circuit illustrated in FIG. 8, themicrocontroller 805 and the fuel gauge 803 can communicate on aperiodic, or near continuous basis, through interface 813 to allow themicrocontroller to receive updates on the charge status of battery 802.

The primary power source 811 can be connected to the battery charger 801at any time during the discharging process. The connection causes thecurrent direction through the battery 802 to reverse and switch from adischarge mode to a charge mode. At or near the instant of the reversalof the current direction through the battery 802, the fuel gauge 803tracks the current into the battery 802 by counting the number ofCoulombs that enter the battery 802 during the charging process.

The charging and discharging processes can be regularly (e.g., periodic,continuous, etc.) monitored using the fuel gauge 803 and microcontroller805. Through regular or continuous monitoring, the microcontroller 805has updated information regarding the energy units remaining in thebattery, which allows a relatively accurate assessment to be made of thestate of battery charge in the battery 802. The state of the batterycharge determined by the microcontroller 805 can then be shown on thedisplay 806. The embodiment shown in display 806 is an icon with fourbars to show the user the state of charge.

A feature that can be included within a portable or battery-poweredmeter is a sleep mode or stand-by mode, which limits the powerconsumption of a meter during periods of non-use or limited use. In theembodiment illustrated in FIG. 8, the microcontroller 805 can be used toplace the circuit into a sleep mode. To limit the power consumption, itcan be desirable for the fuel gauge 803 to be removed from the powerdistribution circuit when the microcontroller 805 places the system intoa sleep mode. A power-switch-control signal 815 from the microcontroller805 to a power switch 814, as illustrate in FIG. 8, can be used toisolate the fuel gauge 803.

The embodiment illustrated in FIG. 8 is beneficial because it allows thepower consumption during a sleep mode to be reduced significantly. Theenergy use by a fuel gauge that continuously monitors the remainingbattery charge can be significant. A continuously operating fuel gauge803, even a low-power fuel gauge, can consume approximately 50-100microamperes, even for a system placed into a sleep mode. Such powerconsumption in a portable battery-powered system, such as a bloodglucose meter, can be considered significant. The microcontroller 805may consume only a few microamperes (e.g., approximately 1-10microamperes), even during a sleep mode.

In certain embodiments, the battery fuel gauge 803 is isolated and notallowed to consume power from a battery when a system is placed in astandby or sleep mode. A power switch 814 can be used to control thepower directed by the voltage regulator 804 to the fuel gauge 803 duringthe discharging process—that is, when the primary power source 811 isdisconnected. The voltage regulator 804 is placed within the circuit forto power the microcontroller 805 and fuel gauge 803 during thedischarging process. The power switch 814 is connected to themicrocontroller 805 so that the microcontroller can send apower-switch-control signal 815 to power switch 814. The power switch814 will then either open or close the circuit that provides power tothe fuel gauge 803. For example, if the microcontroller 805 determinesthat the meter should be entering into a standby or sleep mode, themicrocontroller 805 sends a signal 815 to the power switch 814, whichopens the circuit that directs current to the fuel gauge 803. In theillustration of FIG. 8, the opening of the circuit by way of powerswitch 814 removes a current consumption of approximately 50 to 100microamperes from the battery 802. When the meter returns to an activemode, the microcontroller 805 can send another signal 815 to the powerswitch 814 to close the circuit between the battery 802 and the fuelgauge 803 so that the fuel gauge 803 can resume its function as currentis reintroduced into the fuel gauge system 803.

It is desirable during the standby or sleep mode period for a meter tocontinue assessing the remaining life of a battery 802. For example, inthe case of a blood glucose meter, a user may operate the device daily.It is also possible that the device may not be used, a thus, remain in astandby or sleep mode, for one or more days or for one or more weeks. Inthe embodiment illustrated in FIG. 8, the microcontroller 805 continuesto draw a current of approximately 2 to 3 microamperes while in thesleep mode (e.g., very low power consumption). While the fuel gauge 803can be removed from the power consumption circuit during the sleep mode,as illustrated in FIG. 8, it can be important to track the powerconsumption of the remaining power-drawing components, such as themicrocontroller 805. But, the removal of the fuel gauge 803 from thepower consumption circuit eliminates the fuel gauge 803 operation—thatis the device that tracks current accumulation and consumption.

In certain embodiments, the assessment of remaining battery life orpower consumption during the inactivity of a fuel gauge can be completedusing a processor or microcontroller that includes a power managementroutine. A power management routine can extend the run time of a meterhaving a finite power source, such as, for example, a rechargeablebattery.

In the embodiment of FIG. 8, the microcontroller 805 implementing apower management routine can perform several steps before entering intoa standby or sleep mode. The microcontroller 805 includes a timer, orreceives data from a timer. The timer maintains reference time(s) usedin assessing the remaining charge in the battery 802. The timer maydetermine reference time(s) using a real-time clock. For example, beforeentering into a sleep mode, the microcontroller 805 records thereference time or an actual time along with recording the last state ofthe battery charge. The microcontroller 805 then sends a signal 815 topower switch 814 to open the circuit to fuel gauge 803—that is, removethe fuel gauge 803 from the power consumption loop. With the fuel gauge803 not receiving power, consumption of power from the battery 802 isreduced significantly, but the fuel gauge stops tracking powerconsumption. However, prior to entering the sleep or standby mode, therecording of a reference time by the microcontroller 805 allows thedetermination of power consumption within the meter system after themicrocontroller 805 wakes up. A meter may exit the sleep mode by a userprompting the meter. For example, the user may press a button or apredetermined wake-up criteria may be established for the meter.

After the microcontroller 805 receives a prompt to exit the standby orsleep mode, several operations occur to recalculate and restore the lostcount of battery discharge during the inactivity of the fuel gauge 803.A power-switch-control signal 815 is sent to the power switch 814 toenergize the battery fuel gauge 803. The microcontroller 805 alsodetermines the duration of the standby or sleep mode by subtracting afirst reference time that was recorded when the microcontroller 805entered into the sleep mode currently being exited from a secondreference time, e.g., the time at which the microcontroller wakes up orenters into an active mode. The microcontroller 805 then multiplies thecalculated sleep mode duration by the known sleep mode current andvoltage. The product of the sleep mode duration and the known currentand voltage is the power consumed by the circuit during the standby orsleep mode. The microcontroller 805 then subtracts the calculatedconsumed power from the last recorded known state of batterycharge—e.g., the remaining charge just before the last standby or sleepmode was entered. The result is an estimation of the state of thebattery charge.

FIG. 9 illustrates a finite state machine for a power management methodfor a battery-powered device according to certain embodiments of thepresent application. The power management method can be in the form ofan algorithm or routine implemented on a computer or computerized systemthat monitors the power in a battery-powered device. For example, themethod may be implemented in a system that includes a processor- ormicrocontroller-type device. The method can reduce the average powerconsumption of a fuel gauge integrated circuit while minimizing the lossof information about the exact state of battery charge.

In certain embodiments, a device, such as a meter—e.g., abattery-powered blood glucose meter—can be functioning in a normaloperational state. The meter may be configured to operate in an activemode—e.g., normal mode—and a sleep mode—e.g., standby mode. Startingwith the meter device at normal operation in step 900, a request toenter the sleep mode at step 910 can be received by a microcontroller.The request may occur based on input from a user or the lapse of apre-determined period of time, which triggers the generation of a signalthat is received by a processor or microcontroller. After the requestfor sleep mode at step 910 is received, the processor or microcontrollercan record the time of the request and the state of battery charge atstep 920 at the time of the request. In certain embodiments, the stateof battery charge information will come from data received by theprocessor from a battery fuel gauge, such as the gauge illustrated inFIG. 8. To reduce power consumption during the sleep mode, a powerswitch controlling current to a fuel gauge can be opened to cut thepower off to the fuel gauge. The microcontroller or processor can thenkeep the meter in a sleep mode at step 930 during which powerconsumption may be limited to the microcontroller. While in the sleepmode at step 930, the microcontroller can cycle and wait for the receiptof a signal identifying a wake-up event at step 940. The wake-up eventat step 940 can include, for example, the receipt of an input from auser of the meter, the connection of a primary power source, apre-selected triggering event, etc. After the wake-up event at step 940is received by the microcontroller, the state of battery charge afterthe sleep mode is determined and the state of battery charge from thefuel gauge is updated at step 950. The update to the state of thebattery charge can be determined using the sleep mode duration and thecurrent and voltage that was in the circuit during the sleep mode. Thewake up event at step 940 may also include sending a signal to a powerswitch that energizes the fuel gauge.

The state of battery charge after exiting the sleep mode can bedetermined immediately or shortly after the wake up event at step 940.After the updated state of the battery charge is determined at step 960,the meter can then reenter an mode of normal operation at step 900,e.g., an active mode. During the normal operation of a device at step900, a timer at step 970, such as, for example, a real-time clock, canbe used to allow reference times to be recorded, such as when a circuitchanges between a charge mode, an active discharge mode, or a sleepdischarge mode. During the normal operation mode, the state of batterycharge can be continuously or periodically updated and illustrated on adisplay at step 975 using information received from the fuel gauge.During the normal operation of a device at step 900, such as abattery-powered blood glucose meter, a primary power source may beconnected to a battery charger in the system. Monitoring of the batterycharger can be completed until a signal is sent to the microcontrollerthat the charging is complete at step 980. At this point, another signalcan be sent to update the fuel gauge at step 985 that the battery iscompletely charged. After the signal is sent to update the fuel gauge onthe state of battery charge, the device can then cycle back to a normaloperation mode at step 900.

In certain embodiments, a portable meter having a circuit is configuredwith a battery to provide power to a sensing element within the circuit.The meter includes a processor powered by the circuit. The processor isconfigured to operate the meter in an active mode and a sleep mode. Afuel gauge is powered by the circuit. The fuel gauge is configured totrack state of battery charge data received from the battery duringactive mode operation of the meter. An interface is configured totransfer state of battery charge data from the fuel gauge to theprocessor. A power switch controls current flow to the fuel gauge and isconfigured to be open and closed by the processor. The processor signalsthe power switch into an open position if the meter enters into thesleep mode and the processor signals the power switch into a closedposition if the meter enters into an active mode. Prior to entering thesleep mode, the processor is configured to record a first state ofbattery charge for the battery and a first time reference immediatelyprior to the meter entering said sleep mode. The processor is furtherconfigured to determine a second state of battery charge at a secondreference time immediately after the meter exits from the sleep modeinto the active mode. The second state of battery charge is determinedbased on the recorded first state of charge, the first reference time,the second reference time, and a predetermined energy usage rate of themeter during the sleep mode.

In other embodiments, the portable meter is a blood glucose meter. Thefuel gauge can continuously track the state of battery charge during theactive mode of operation of the meter. The fuel gauge can be anintegrated circuit. The portable meter can further include a displaycoupled to the processor in which the display is configured to displaythe present state of battery charge. The processor can be amicrocontroller. The battery can be a rechargeable battery. The portablemeter can enter into the active mode when a primary power source ischarging the battery.

According to another embodiment, a method of power management includes abattery-powered meter that is configured to operate in an active modeand a standby mode. The batter-powered meter includes a battery fuelgauge and a microcontroller. The method includes the steps of receivinga first request to enter into the standby mode. A first state of chargeis recorded for a battery of the meter. The recording occurs at a firstreference time immediately after the first request is received. Thefirst reference time is recorded using the microcontroller. The meter isentered into the standby mode with the power to the battery fuel gaugebeing switched off in the standby mode. A second request to exit thestandby mode and enter the active mode is received at a second referencetime. The second reference time occurs after the first reference time.In response to the second request, a second reference time isimmediately recorded and the microcontroller determines a second stateof battery charge based on the first reference time, the secondreference time, a standby mode current, and a standby mode voltage ofthe meter.

In other embodiments, the first state of battery charge for the batteryis determined using the battery fuel gauge. The battery-powered metercan be initially operating in an active mode. If the meter is in anactive mode, a state of battery charge can be updated using batterycharge data received by the microcontroller from the battery fuel gauge.Updating can be continuous. The state of battery charge can be displayedon a display gauge.

According to a further embodiment, a computer-readable memory medium hasstored thereon instructions for managing the power of a battery-poweredmeter operating in an active mode and a sleep mode. The instructionsincludes the steps of receiving a first request to enter into the sleepmode and recording a first state of charge for a battery of the meter.The recording occurs at a first reference time immediately after thefirst request is received. A first reference time is recorded. The meteris entered into the standby mode wherein power to a battery fuel gaugeis switched off in the standby mode. A second request is received at asecond reference time to exit the sleep mode and enter the active mode.The second reference time occurs after the first reference time.Immediately after the second request, a second reference time isrecorded. A second state of battery charge is determined based on thefirst reference time, the second reference time, a sleep mode current,and a sleep mode voltage.

In certain embodiments, a meter may incorporate multiple operations,such as, for example, a blood glucose concentration testing operationand global positioning systems. Such multiple operations on a portablemeter may require additional power from a battery. The powerrequirements can be supplied using a larger battery, efficient powermanagement techniques, or a combination of both.

While the invention has been described with reference to details of theillustrated embodiments, these details are not intended to limit thescope of the invention as defined in the appended claims. For example,the rapid charge system for the battery may be used in variousheat-sensitive applications. The disclosed embodiments and obviousvariations thereof are contemplated as falling within the spirit andscope of the claimed invention.

What is claimed is:
 1. A blood-glucose meter adapted to determine ablood-glucose concentration of a fluid sample, the meter comprising: ahousing defining a port sized to receive at least a portion of a testsensor; a rechargeable power source at least partially disposed withinthe housing; and one or more processors disposed within said housing,said one or more processors configured to implement a charge process forcharging the rechargeable power source, said charge process includingrapid charging of said recharageable power source at a first charge rateuntil a first predetermined event occurs and thereafter charging saidrechargeable power source at a second charge rate that is lower thansaid first charge rate, wherein implementation of said charge processminimizes temperature rise in said meter such that said temperature riseis negligible to a temperature-sensitive blood-glucose concentrationtest.
 2. The meter of claim 1, wherein the negligible temperature riseis a temperature rise of less than one degree Celsius.
 3. The meter ofclaim 1, wherein said first charge rate is about 1C.
 4. The meter ofclaim 1, wherein said second charge rate is less than 1C.
 5. The meterof claim 1, wherein said second charge rate is from about 0.5C to about0.6C.
 6. The meter of claim 1, wherein said first predetermined event isa lapsing of a predetermined time period.
 7. The meter of claim 6,wherein said predetermined time period is about one minute or less. 8.The meter of claim 1, wherein at least one of said one or moreprocessors comprises an integrated circuit.
 9. The meter of claim 1,wherein said housing has a footprint area of less than about nine squareinches.
 10. The meter of claim 1, wherein said housing has a longdimension of less than approximately three inches.
 11. The meter ofclaim 1, further comprising implementing a human-perceivable signalfollowing said first predetermined event.
 12. A blood-glucose meteradapted to determine a blood-glucose concentration of a fluid sample,the meter comprising: a housing defining a port sized to receive atleast a portion of a test sensor; a rechargeable power source at leastpartially disposed within the housing; and one or more processorsdisposed within said housing, said one or more processors configured toimplement a charge routine comprising rapid charging of saidrechargeable power source at a first charge rate until a firstpredetermined event occurs and thereafter charging said rechargeablepower source at a second charge rate that is lower than said firstcharge rate, wherein implementation of said charge routine is inaccordance with temperature rise criteria for said meter in view ofparticular temperature sensitive blood-glucose concentration tests forwhich said meter is configured.
 13. The meter of claim 12, wherein thecharge routine causes a negligible temperature rise of less than onedegree Celsius in the rechargeable power source.
 14. The meter of claim12, wherein said second charge rate is less than 1C.
 15. The meter ofclaim 12, wherein said first predetermined event is a lapsing of aboutone minute or less.
 16. The meter of claim 12, wherein said housing hasa long dimension of less than approximately three inches.
 17. A bloodglucose meter adapted to determine a blood-glucose concentration of afluid sample, the meter comprising: a housing defining a port sized toreceive at least a portion of a test sensor; a rechargeable power sourceat least partially disposed within the housing; and one or moreprocessors disposed within said housing, said one or more processorsconfigured to implement a charge process comprising rapid charging ofsaid rechargeable power source at a first charge rate until a firstpredetermined event occurs and thereafter charging said rechargeablepower source at a second charge rate that is lower than said firstcharge rate, wherein implementation of said charge process causes anegligible temperature rise in the rechargeable power source due to thefirst and second charge rates, thereby limiting temperature effects indetermining a blood-glucose concentration of the fluid sample.
 18. Thebattery-power meter of claim 17, wherein the negligible temperature riseis a temperature rise of less than one degree Celsius in therechargeable power source.
 19. The meter of claim 17, wherein saidsecond charge rate is less than 1C.
 20. The meter of claim 17, whereinsaid housing has a long dimension of less than approximately threeinches.